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Solution: Count Substrings With K-Frequency Characters II

Explore how to count substrings where at least one character appears k times using the sliding window pattern. Understand the two-pointer approach to efficiently track character frequencies and dynamically adjust the window to find all valid substrings, optimizing both time and space complexities.

Statement

Given a string s and an integer k, return the total number of substrings of s where at least one character appears at least k times.

Note: A substring is a contiguous sequence of characters within a string. For example, "edu" is a substring of "educative". 

Constraints:

  • 11 \leq ...